In 1786 James Symington, then joint-engineer with his brother George, to the Wanlockhead Mines, was struck with the idea which, as we have seen, several other ingenious minds were also busy with about the same time,--of rendering the steam-engine available for locomotion both on land and sea. After much study and reflection, he succeeded in embodying the idea in a working model. It was supported on four wheels, which were moved in any direction by means of a small steam-engine, and could carry 16 cwt., besides coals, water, &c. It was exhibited in Edinburgh in the summer of 1786, and made a considerable sensation. Mr. Miller, fond of all such inventions, did not fail to get a sight of Symington's locomotive engine, the first time he was in town. He was delighted with its ingenuity and completeness, and procured an interview with the author. Of course, Miller was full of his own experiments, and told Symington the whole story of his efforts to propel vessels by paddle-wheels, and the want of some stronger, and more constant power than that of men to turn the capstan, upon which the motion of the wheels depended. Symington at once expressed the opinion he had formed,--that steam was equally available for vessels as for carriages, and showed him how the steam-engine which he had devised for his locomotive could be applied to the paddle-wheels. Miller was so much struck by his statements, which he illustrated by reference to the model, that he determined to have an engine made on the same plan, and fitted into one of his double boats. Accordingly, an engine was built under Symington's directions and superintendence, sent to Dalswinton, and put together in October 1788. The engine, in a strong oak frame, was placed in the one half of a double pleasure-boat, the boiler occupying the other half, and the paddle-wheels being fixed in the middle.